The present invention relates to an audio device that processes and adds various effects to audio signals including tone signals of an electronic musical instrument, an electric guitar, and the like, and more particularly to an improvement of a bypass function for outputting original audio signals by temporarily bypassing an effector when an effect parameter is changed.
Conventionally, there have been employed audio devices, which process tone signals or audio signals of such tone signals in a broad sense in electronic musical instruments, electric guitars, and the like, or in guitar amplifiers or the like, and which impart various effects to those signals (may be simply referred to as the “effector” hereinafter). In such effectors, various tonal or audio effects can be selected from among distortion that distorts sound, reverb that adds reverberation effect, echo that adds delay to the original sound such that the original sound is repeated as it fades away in a distance like an “echo,” flanger that modulates the quality of the original sound (frequency distribution), wahwah that transmits frequency components of only a specific range so as to make a sound boxy or clear, and the like, while settings of parameters of the respective effects can be changed at any time. Such effects are selected and set, as needed, by an artist or the like for various purposes such as improving sound quality of the original sound and enhancing the live feel.
This type of effector is usually configured by digital signal processing such as a DSP, and in the case of switching a type of effect to be imparted, changing a value of a parameter in the effect, or the like, it is necessary to execute such a process as clearing stored data or redoing an operation. Such a process carried out for making the change require a certain amount of time, during which the sound may be interrupted or unpleasant noise may be generated. That is, just changing the parameter value discontinuously and largely results in generation of noise, even if the type of effect are not switched. Also, in the case of a delay-type effect, an audio signal for a plurality of samples are stored in a storage device called “delay line,” such that data for the plurality of samples in the delay line need to be initialized when an effect changing process is performed, and therefore a selected effect does not function properly during a certain amount of time. In addition, the effect does not function properly for a certain amount of time at the time of replacement of the microcode that is executed by the DSP during the effect changing process. It is not preferable that sound is interrupted or noise is generated during the effect changing process.
To deal with this problem, conventionally, as disclosed in Japanese Patent Publication No. Hei 7-69690 (hereinafter referred to as Patent Literature 1), a bypass channel that outputs an original audio signal by bypassing a signal processing circuit for performing effect processing is provided so that the audio signal is output from the bypass channel during a time period required for the effect changing process, and after the time period has terminated a source of an audio signal to be output is switched back to the signal processing circuit. Accordingly, interruption of sound and generation of unpleasant noise are prevented from occurring during the period when the effect changing process is carried out.
Further, Japanese Unexamined Patent Application Publication No. Hei 8-30271 (hereinafter referred to as Patent Literature 2) discloses an effector, similarly to the aforementioned Patent Literature 1, in which, in addition to a bypass channel that outputs an original audio signal without passing through a signal processing circuit for performing effect processing (a filter and a reverberator in FIG. 1 of the Patent Literature 2), an adder for adding signals output via the filter or reverberator to the signal output via the bypass channel is further provided. In this effector, it is determined whether the effect changing process leads to generation of noise, and if it is determined that the effect changing process does lead to generation of noise, an output signal output through the filter and reverberator is controlled to prevent unpleasant noise that is generated during the effects changing process from being output.
In the above-described Patent Literatures 1 and 2, some improvement can be seen in terms of interruption of sound and generation of noise during the effect changing process. However, sense of discomfort one feels may be increased in some cases by adopting only a configuration in which the output signal is switched from the signal output via the signal processing circuit for performing effect processing to the signal output via the bypass channel instead of the signal processing circuit, during the period required for the effect changing process.
The tonal or audio effects, described above, include distortion, reverb, echo, flanger, and the like. In the case of a type change between effect types which does not involve a noticeable change in terms of signal levels and frequency characteristics after adding an effect to the original sound, such as the delay-type effects including reverb and echo, for example, problems many not arise even if switching of the output signals is merely performed as mentioned above. However, switching the signals, as mentioned above is not enough in the case where a tone volume is set within the signal processing circuit or in the case where an equalizer is set to be used. That is, in the case where the tone volume is set within the signal processing circuit or in the case where an equalizer is set to be used, one may feel a sense of much discomfort if a large sound is suddenly output as a result of switching from the signal output via the effects processing to the original audio signal output via the bypass channel.
Further, in the case of a type change between effect types such as distortion-type effects and wahwah, which are subject to a drastic change in signal levels and frequency characteristics, as compared to the original sound, after effects are imparted thereto, and particularly in the case of a type change between two effect types that results in a reduced volume in terms of a sense of hearing, one may feel a sense of much discomfort if a large sound is suddenly output as a result of switching from the signal output via the effects processing to the original audio signal output via the bypass channel.